If alpha + beta = 5 and alpha^3+beta^3= 35, find the quadratic equation whose roots are Alpha and beta
Answers
Answer:
Quadratic equation is x² - 5x + 6
it is given that,
α + β = 5 and α³ + β³ = 35
then we have to find the quadratic equation whose roots are α and β.
as α³ + β³ = 35
⇒(α + β)³ - 3αβ(α + β) = 35
⇒(5)³ - 3αβ(5) = 35
⇒125 - 35 = 15αβ
⇒90 = 15αβ
⇒αβ = 6
now, quadratic equation is given
x² - (sum of roots)x + product of roots
⇒x² - (α + β)x + αβ
⇒x² - 5x + 6
Given
➡️alpha + beta = 5
➡️alpha³ + beta³ = 35
[ use formula ]
♦️( a + b )³ = a³ + b³ + 3ab ( a + b )
let
⚡a = alpha
⚡b = beta
➡️( alpha + beta )³ = alpha³ + beta³ + 3.alpha.bera ( alpha + beta )
[ substitute the above values in above formula ]
⭐( 5 )³ = 35 + 3.alpha.beta ( 5 )
⭐125 = 35 + 3.alpha.beta ( 5 )
⭐125 - 35 = 3.alpha.beta ( 5 )
⭐90 = 3.alpha.beta ( 5 )
⭐alpha × beta = 6
➡️➡️➡️➡️➡️The quadratic equation is x² - ( alpha + beta )x + alpha × beta
:. x² - 5x + 6